Resource Pooling in a Blade Cluster Switching Center Server

1. A switching center server comprising: a blade cluster including a plurality of blades that have access to a plurality of resource pools for handling a call, wherein resources in any given one of the resource pools comprise resources at a media gateway that are switched under the control of the switching center server; and a master for each resource pool, each master provided on one of the blades and configured to centrally coordinate the blades' use of resources in the corresponding resource pool.

2. The switching center server according to claim 1 , wherein two different blades provide information about the used resources for said call.

3. The switching center server according to claim 1 , further comprising a call controller provided on one of the blades and configured to control resources for said call.

4. The switching center server according to claim 3 , further comprising a buddy for one of the masters and residing on a different blade than the corresponding master, the buddy containing the information about the resources controlled by a call controller residing on the same blade as the master.

5. The switching center server according to claim 4 , further comprising a coordinator configured, if a blade fails, to: create at least one of a new master as a replacement for a master present on the failed blade and a new buddy as a replacement for a buddy present on the failed blade; and allocate the new master, if created, to a first blade in said blade cluster; and allocate the new buddy, if created, to a second blade in said blade cluster.

6. The switching center server according to claim 5 , wherein, if the coordinator creates a new master on the first new blade, the other blades transmit a list of used resources for said call to the new master.

7. The switching center server according claim 5 , wherein the coordinator detects the signaling load of the blades and moves the masters and buddies for different resource pools to different blades depending on the signaling load of the different blades.

8. The switching center server according to claim 1 , wherein each blade further comprises a blade status information unit configured to determine the status of the blade and to inform the other blades of any blade status changes.

9. The switching center server according to claim 1 , wherein each blade comprises a blade recovery unit configured, if the blade fails, to carry out a blade recovery procedure, the blade recovery unit configured to decide which calls handled by the failed blade to retain and to transmit information indicating the resources used for those calls to the corresponding master.

10. The switching center server according to claim 1 , wherein each blade comprises a group communication service unit configured to control delivery of messages to other blades, the messages being delivered to each blade in the same order.

11. The switching center server according to claim 1 , comprising a route master for each route of a trunk, or an access master for each Integrated Digital Service Network (ISDN) access.

12. The switching center server according to claim 11 , further comprising a call controller provided on one of the blades and configured to control resources for said call, requesting control over resources from the route master or access master and returning control when the resources are no longer needed.

13. The switching center server according to claim 1 , further comprising a media gateway master configured to control handling of maintenance messages of a media gateway.

14. A method for controlling a switching center server, the server having a blade cluster with a plurality of blades, wherein the plurality of blades have access to a plurality of resource pools for handling a call, wherein resources in any given one of the resource pools comprise resources at a media gateway that are switched under the control of the switching center server, the method comprising, for each resource pool, coordinating the blades' use of resources in the pool at a master dedicated to that pool.

15. The method according to claim 14 , wherein the switching center server comprises a route master for each route of a trunk, or an access master for each Integrated Digital Service Network (ISDN) access, and further comprises a call controller configured to control resources for a call, and wherein the method further comprises performing at the call controller at least one of: setting up said call, supervising said call, disconnecting said call, and requesting control over resources from the route master or access master, and returning control when the resources are no longer needed.

16. The method according to claim 15 , wherein the method comprises providing information about the used resources present on a first blade where the call controller resides on a second blade.

17. The method according to claim 14 , further comprising detecting a status change of at least one of the blades, and, if such a change is detected, informing the other blades of that change.

18. The method according to claim 14 , further comprising detecting failure of a blade, and detecting whether a recovery procedure is carried out for the failed blade, wherein the recovery procedure retains calls handled by the failed blade and continues to use the resources for such call controlled by the failed blade.

19. The method according to claim 14 , further comprising: detecting failure of a blade, and detecting whether a recovery procedure is carried out for the failed blade, wherein the recovery procedure transmits information to the corresponding master indicating resources used by the failed blade for calls not retained upon recovery, thereby enabling the master to reset those resources.

20. The method according to claim 14 , further comprising: detecting failure of a blade on which a master is present; creating a new master on a new blade as a replacement for the master present on the failed blade; and transmitting, from each of the other blades to the new master, a first list of resources used by the other blade.

21. The method according to claim 20 , wherein a call controller resides on the failed blade, said method further comprising: transmitting, from a buddy for the master on the failed blade to said new master, a second list of resources used by the master on the failed blade.

22. The method according to claim 21 , further comprising resetting resources not present on said first or second lists of resources.

23. The method according to claim 22 , wherein resetting resources not present on said first or second lists of resources is performed when no recovery procedure is performed that may result in continuous use of the resources.

24. The method according to claim 14 , further comprising: detecting whether more than one blade is in an active state; and if so, creating a buddy on a first one of the blades for a master on a second one of the blades.

25. The method according to claim 14 , further comprising: detecting failure of a blade on which a master is present; creating a new master on a new blade, as a replacement for the master present on the failed blade; and creating a new buddy for the new master.

26. The method according to claim 14 , further comprising: detecting failure of a blade on which a buddy is present; creating a new buddy on a new blade, as a replacement for the buddy present on the failed blade.

27. The method according to claim 14 , wherein the switching center server further comprise a coordinator, and wherein the method further comprises: detecting failure of a blade on which a master is present; creating a new master on a new blade, as a replacement for the master present on the failed blade, said creation comprising at least one of: determining, by the coordinator, on which blade the new master is created, transmitting, from the coordinator to other blades, information indicating that the new master is being created, building, by the new master, a status table of resources used by each blade, transmitting, from the other blades to the new master, information needed by the new master for coordinating the blades' usage of the pooled resources, transferring, from said new master to a buddy, a copy of data related to calls controlled by said new blade, transmitting, from said buddy to said new master, information indicating that that the buddy has successfully stored said data, transmitting, from the new master to the other blades, information indicating that creation of the new master is completed.

28. The method according to claim 27 , further comprising buffering seizure requests for resources received during migration of the master and, after completion of the transfer, transmitting the buffered seizure requests to the new master.

29. The method according to claim 28 , further comprising: detecting failure of a blade on which the new master is provided before completion of the migration; and responsive to said detection, aborting the migration of the master.

30. The method according to claim 14 , wherein the switching center server further comprise a buddy for the master and a coordinator, and wherein the method further comprises: detecting failure of the blade on which said buddy is present, determining at the coordinator to which blade the buddy should be migrated, and creating a new buddy on that blade, transmitting from the master to the new buddy all data needed by the new buddy, transmitting from the buddy to other blades information that informs the other blades that the buddy has been migrated to the new buddy, and sending from the master to the new buddy, after the master has been informed of the transfer, information indicating changed seizure states.

31. The method according to claim 14 , wherein the switching center server further comprises a buddy for the master and a coordinator, wherein the coordinator is configured to create at least one of a new master and new buddy when a blade fails, and wherein the method comprises moving said coordinator from a first blade to a second blade without changing the coordinator's control over the creation of said new master or new buddy.

32. The method according to claim 14 , wherein the switching center server further comprises buddies for one or more masters, and wherein the method further comprises: detecting activation of a new blade, and transmitting from another blade to the new active blade the current status and the allocation of masters and buddies.